It's kinda like marbling paper, fun but you have to let go of having total control. I still have never gotten anything that looks like the stuff Mudbutt does. I think it has to do with the dodge tool. But it's also kind of cool to see how varied the results are from different users. Pun intended. Wish I could combine Lascaux and Chibi. Now that would be fun.

It results in forcing you to see more accurately what you're looking at rather than drawing a preconceived notion of what something looks like. Everyone does that unconsciously. I'm sure you can get 'Drawing on the Right Side of the Brain' by Betty Edwards from your local library. http://www.amazon.com/The-Drawing-Right-Side-Brain/dp/0874774241